The population of Ireland is about 6.3 million, but it is estimated that 50 to 80 million people around the world have Irish forebears, making the Irish diaspora one of the biggest of any nation. Historically, emigration from Ireland has been the result of conflict, famine and economic issues. People of Irish descent are found mainly in English-speaking countries, especially the United Kingdom, the United States, Canada and Australia. There are also significant numbers in Argentina, Mexico and New Zealand. The United States has the most people of Irish descent, while in Australia those of Irish descent are a higher percentage of the population than in any other country outside Ireland.[16] Many Icelanders have Irish and Scottish Gaelic forebears.[17]

During the past 10,000 years of inhabitation, Ireland has witnessed some different peoples arrive on its shores. The ancient peoples of Ireland—such as the creators of the Céide Fields and Newgrange—are almost unknown. Neither their languages nor terms they used to describe themselves have survived. As late as the middle centuries of the 1st millennium the inhabitants of Ireland did not appear to have a collective name for themselves.

Scotland takes its name from Scota, who in Irish mythology, Scottish mythology, and pseudohistory, is the name given to two different mythological daughters of two different Egyptian Pharaohs to whom the Gaels traced their ancestry, allegedly explaining the name Scoti, applied by the Romans to Irish raiders, and later to the Irish invaders of Argyll and Caledonia which became known as Scotland. Other Latin names for people from Ireland in Classic and Mediaeval sources include Attacotti and Gael. This last word, derived from the Welshgwyddel "raiders", was eventually adopted by the Irish for themselves. However, as a term it is on a par with Viking, as it describes an activity (raiding, piracy) and its proponents, not their actual ethnic affiliations.

The GreekmythographerEuhemerus originated the concept of Euhemerism, which treats mythological accounts as a reflection of actual historical events shaped by retelling and traditional mores. In the 12th century, Icelandicbard and historian Snorri Sturluson proposed that the Norse gods were originally historical war leaders and kings, who later became cult figures, eventually set into society as gods. This view is in agreement with Irish historians such T. F. O'Rahilly and Francis John Byrne; the early chapters of their respective books, Early Irish history and mythology (reprinted 2004) and Irish Kings and High-Kings (3rd revised edition, 2001), deal in depth with the origins and status of many Irish ancestral deities.

One legend states that the Irish were descended from one Míl Espáine, whose sons supposedly conquered Ireland around 1000 BC or later.[19] The character is almost certainly a mere personification of a supposed migration by a group or groups from Iberia to Ireland. It is from this that the Irish were, as late as the 1800s, popularly known as "Milesian".[20] Medieval Irish historians, over the course of several centuries, created the genealogicaldogma that all Irish were descendants of Míl, ignoring the fact that their own works demonstrated inhabitants in Ireland prior to his supposed arrival.

However, this haplogroup is now believed by some to have originated over 12,000 years more recently than previously thought.[24] It thus follows that Irish and many other R1b subclades will be considerably younger than the maximum age of 18,000 years. The previous estimates, based on inaccurate dating methods (30,000+ years BP), made R1b and its subclades seem to be more useful indicators of the paleolithic era populations of western Europe than they actually are. According to recent 2009 studies by Bramanti et al. and Malmström et al. on mtDNA,[25][26] related western European populations appear to be largely from the neolithic and not paleolithic era, as previously thought. There was discontinuity between mesolithic central Europe and modern European populations mainly due to an extremely high frequency of haplogroup U (particularly U5) types in mesolithic central European sites.

The existence of an especially strong genetic association between the Irish and the Basques, one even closer than the relationship between other west Europeans, was first challenged in 2005,[27] and in 2007 scientists began looking at the possibility of a more recent Mesolithic- or even Neolithic-era entrance of R1b into Europe.[28] A new study published in 2010 by Balaresque et al. implies either a Mesolithic- or Neolithic- (not Paleolithic) era entrance of R1b into Europe.[29] However, all these genetic studies are in agreement that the Irish and Basque (along with the Welsh) share the highest percentage of R1b populations. A recent whole genome analysis of 1 neolithic and 3 Bronze Age skeletal remains in Ireland suggested that the original farming population was mostly similar to present day Sardinians and the 3 Bronze Age remains had a Steppe component to their genetics showing links with Eastern Europe. Most modern Irish share more DNA with the 3 Bronze Age men from Rathlin than the earlier Ballynahatty neolithic woman.[30][31]

A recent genetic study done on the Irish show that they have two main ancestry sources a French component (mostly northwestern French) and West Norwegian from the Viking era. [32][33]

Black Irish is an ambiguous term sometimes used (mainly outside Ireland) as a reference to a dark-haired phenotype appearing in people of Irish origin.[34] However, dark hair in people of Irish descent is common, although darker skin complexions appear less frequently.[35] One popular speculation suggests the Black Irish are descendants of survivors of the Spanish Armada, despite research discrediting such claims.[36] In Bob Quinn's documentary series Atlantean, he explores an alternative 'Iberian' hypothesis, proposing the existence of an ancient sea-trading route skirting the Atlantic coast from North Africa and the Iberian Peninsula to regions such as Connemara. While preferring the term "The Atlantean Irish", Quinn's reference to certain phenotypical characteristics (within elements of the Irish populace and diaspora) as possible evidence of a previous Hibernian-Iberian (and possibly Berber) admixture mirrors common descriptions of the Black Irish.[37]

The term has also come to be used to refer to the African-Irish descendants of those who live on Barbados and Montserrat,[38] a number of whom have Irish surnames, still retain part of their Irish accents and sing bilingual songs.[39]

One Roman historian records that the Irish people were divided into "sixteen different nations" or tribes.[40] Traditional histories assert that the Romans never attempted to conquer Ireland, although it may have been considered.[40] The Irish were not, however, cut off from Europe; they frequently raided the Roman territories,[40] and also maintained trade links.[41]

The introduction of Christianity to the Irish people during the 5th century brought a radical change to the Irish people's foreign relations.[43] The only military raid abroad recorded after that century is a presumed invasion of Wales, which according to a Welsh manuscript may have taken place around the 7th century.[43] In the words of Seumas MacManus:

If we compare the history of Ireland in the 6th century, after Christianity was received, with that of the 4th century, before the coming of Christianity, the wonderful change and contrast is probably more striking than any other such change in any other nation known to history.[43]

Following the conversion of the Irish to Christianity, Irish secular laws and social institutions remained in place.[44]

The 'traditional' view is that, in the 4th or 5th century, Gaelic language and culture was brought to Scotland by settlers from Ireland, who founded the Gaelic kingdom of Dál Riata on Scotland's west coast.[45][46] This is based mostly on medieval writings from the 9th and 10th centuries. The archaeologist Ewan Campbell argues against this view, saying that there is no archeological or placename evidence for a migration or a takeover by a small group of elites. He states that "the Irish migration hypothesis seems to be a classic case of long-held historical beliefs influencing not only the interpretation of documentary sources themselves, but the subsequent invasion paradigm being accepted uncritically in the related disciplines of archaeology and linguistics."[47] Dál Riata and the territory of the neighbouring Picts merged to form the Kingdom of Alba, and Gaelic language and culture became dominant there. The country came to be called Scotland, after the Roman name for the Gaels: Scoti. The Isle of Man and the Manx people also came under massive Gaelic influence in their history.

Common to both the monastic and the secular bardic schools were Irish and Latin. With Latin, the early Irish scholars "show almost a like familiarity that they do with their own Gaelic".[49] There is evidence also that Hebrew and Greek were studied, the latter probably being taught at Iona.[50]

"The knowledge of Greek", says Professor Sandys in his History of Classical Scholarship, "which had almost vanished in the west was so widely dispersed in the schools of Ireland that if anyone knew Greek it was assumed he must have come from that country."'[51]

The influx of Viking raiders and traders in the 9th and 10th centuries resulted in the founding of many of Ireland's most important towns, including Cork, Dublin, Limerick, and Waterford (earlier Gaelic settlements on these sites did not approach the urban nature of the subsequent Norse trading ports). The Vikings left little impact on Ireland other than towns and certain words added to the Irish language, but many Irish taken as slaves inter-married with the Scandinavians, hence forming a close link with the Icelandic people. In the Icelandic Laxdœla saga, for example, "even slaves are highborn, descended from the kings of Ireland."[54] The first name of Njáll Þorgeirsson, the chief protagonist of Njáls saga, is a variation of the Irish name Neil. According to Eirik the Red's Saga, the first European couple to have a child born in North America was descended from the Viking Queen of Dublin, Aud the Deep-minded, and a Gaelic slave brought to Iceland.[15]

The Irish were among the first people in Europe to use surnames as we know them today.[55] It is very common for people of Gaelic origin to have the English versions of their surnames beginning with 'Ó' or 'Mac' (Over time however many have been shortened to 'O' or Mc). 'O' comes from the Gaelic Ó which in turn came from Ua, which means "grandson", or "descendant" of a named person. Mac is the Gaeilge for son.

Names that begin with Mac or Mc include Mac Cárthaigh (MacCarthy), Mac Diarmada (MacDermott), Mac Domhnaill (MacDonnell), and Mac Mathghamhna (MacMahon) Mag Uidhir (Maguire). Mac is commonly anglicised Mc. However, "Mac" and "Mc" are not mutually exclusive, so, for example, both "MacCarthy" and "McCarthy" are used. While both "Mac" and "Ó'" prefixes are Gaelic in origin, "Mac" is more common in Scotland and in Ulster than in the rest of Ireland; furthermore, "Ó" is far less common in Scotland than it is in Ireland. The proper surname for a woman in Irish uses the feminine prefix nic (meaning daughter) in place of mac. Thus a boy may be called Mac Domhnaill whereas his sister would be called Nic Dhomhnaill or Ní Dhomhnaill – the insertion of 'h' follows the female prefix in the case of most consonants (bar H, L, N, R, & T).

A son has the same surname as his father. A female's surname replaces Ó with Ní (reduced from Iníon Uí – "daughter of the grandson of") and Mac with Nic (reduced from Iníon Mhic – "daughter of the son of"); in both cases the following name undergoes lenition. However, if the second part of the surname begins with the letter C or G, it is not lenited after Nic.[citation needed] Thus the daughter of a man named Ó Maolagáin has the surname Ní Mhaolagáin and the daughter of a man named Mac Gearailt has the surname Nic Gearailt. When anglicised, the name can remain O' or Mac, regardless of gender.

There are a number of Irish surnames derived from Norse personal names, including Mac Suibhne (Sweeney) from Swein and McAuliffe from "Olaf". The name Cotter, local to County Cork, derives from the Norse personal name Ottir. The name Reynolds is an Anglicization of the Gaelic Mac Raghnaill, itself originating from the Norse names Randal or Reginald. Though these names were of Viking derivation some of the families who bear them appear to have had Gaelic origins.

"Fitz" is an old Norman French variant of the Old French word fils (variant spellings filz, fiuz, fiz, etc.), used by the Normans, meaning son. The Normans themselves were descendants of Vikings, who had settled in Normandy and thoroughly adopted the French language and culture.[57] With the exception of the Gaelic-Irish Fitzpatrick (Mac Giolla Phádraig) surname, all names that begin with Fitz – including FitzGerald (Mac Gearailt), Fitzsimons (Mac Síomóin/Mac an Ridire) and FitzHenry (Mac Anraí) – are descended from the initial Norman settlers. A small number of Irish families of Gaelic origin came to use a Norman form of their original surname—so that Mac Giolla Phádraig became Fitzpatrick—while some assimilated so well that the Gaelic name was dropped in favor of a new, Hiberno-Norman form. Another common Irish surname of Norman Irish origin is the 'de' habitational prefix, meaning 'of' and originally signifying prestige and land ownership. Examples include de Búrca (Burke), de Brún, de Barra (Barry), de Stac (Stack), de Tiúit, de Faoite (White), de Londras (Landers), de Paor (Power). The Irish surname "Walsh" (in Gaelic Breathnach) was routinely given to settlers of Welsh origin, who had come during and after the Norman invasion. The Joyce and Griffin/Griffith (Gruffydd) families are also of Welsh origin.

The Mac Lochlainn, Ó Maol Seachlainn, Ó Maol Seachnaill, Ó Conchobhair, Mac Loughlin and Mac Diarmada families, all distinct, are now all subsumed together as MacLoughlin. The full surname usually indicated which family was in question, something that has been diminished with the loss of prefixes such as Ó and Mac. Different branches of a family with the same surname sometimes used distinguishing epithets, which sometimes became surnames in their own right. Hence the chief of the clan Ó Cearnaigh (Kearney) was referred to as An Sionnach (Fox), which his descendants use to this day. Similar surnames are often found in Scotland for many reasons, such as the use of a common language and mass Irish migration to Scotland in the late 19th and early to mid-20th centuries.

The Irish people of the Late Middle Ages were active as traders on the European continent.[58] They were distinguished from the English (who only used their own language or French) in that they only used Latin abroad—a language "spoken by all educated people throughout Gaeldom".[59] According to the writer Seumas MacManus, the explorer Christopher Columbus visited Ireland to gather information about the lands to the west,[60] a number of Irish names are recorded on Columbus' crew roster preserved in the archives of Madrid and it was an Irishman named Patrick Maguire who was the first to set foot in the Americas in 1492;[60] however, according to Morison and Miss Gould[clarification needed], who made a detailed study of the crew list of 1492, no Irish or English sailors were involved in the voyage.[61]

An English report of 1515 states that the Irish people were divided into over sixty Gaelic lordships and thirty Anglo-Irish lordships.[44] The English term for these lordships was "nation" or "country".[44] The Irish term "oireacht" referred to both the territory and the people ruled by the lord.[44] Literally, it meant an "assembly", where the Brehons would hold their courts upon hills to arbitrate the matters of the lordship.[44] Indeed, the Tudor lawyer John Davies described the Irish people with respect to their laws:

There is no people under the sun that doth love equal and indifferent (impartial) justice better than the Irish, or will rest better satisfied with the execution thereof, although it be against themselves, as they may have the protection and benefit of the law upon which just cause they do desire it.[62]

Another English commentator records that the assemblies were attended by "all the scum of the country"—the labouring population as well as the landowners.[44] While the distinction between "free" and "unfree" elements of the Irish people was unreal in legal terms, it was a social and economic reality.[44] Social mobility was usually downwards, due to social and economic pressures.[44] The ruling clan's "expansion from the top downwards" was constantly displacing commoners and forcing them into the margins of society.[44]

Many Gaelic Irish were displaced during the 17th century plantations. Only in the major part of Ulster did the plantations of mostly Scottish prove long-lived; the other three provinces (Connacht, Leinster, and Munster) remained heavily Gaelic Irish. Eventually, the Anglo-Irish and Protestant populations of those three provinces decreased drastically as a result of the political developments in the early 20th century in Ireland, as well as the Catholic Church's Ne Temere decree for mixed marriages, which obliged the non-Catholic partner to have the children raised as Catholics[citation needed].

Known as An Górta Mór (The great hunger) in Gaeilge, millions of Irish people died and emigrated during Ireland's largest famine. The famine lasted from 1845 - 1849, it was worst during 1847 which was known as Black '47. The famine occurred due to the extremely impoverished Irish population's staple food the potato being infected with Blight. This meant the crop failed and turned black. Starving people who tried to eat them would only vomit it back up soon afterwards. Soup kitchens were set up but made little difference. The English government produced little aid. Sending raw corn known as 'Peel's Brimstone' to Ireland. It was known by this name after the British PM at the time and the fact that native Irish weren't aware on how to cook corn. This led to little or no improvement. The British government set up workhouses which were disesase ridden (with cholera, TB and others) but they also failed as little food was available and many died on arrival as they were overworked. Some English political figures at the time saw the famine as a purge from God to exterminate the majority of the native Irish population.

Irish people emigrated to escape the famine journeying predominantly to the east coast of the US especially Boston and New York, Liverpool in England, Australia, Canada and New Zealand. Many records show the majority of emigrants to Australia were in fact prisoners sent to assist in the construction of English colonies there. A substantial proportion of these committed crimes in hopes of being extradited to Australia. Favouring it to the persecution and hardships they endured in their homeland. Emigrants travelled on 'Coffin Ships' they were called this as there were high mortality rates on board. Many died of disease or starved. Conditions on board were abysmal - tickets were expensive so stowaways were common, little food stuff was given to passengers who were simply viewed as cargo in the eyes of the ship workers. Famous coffin ships include the Jeanie Johnston and the Dunbrody.

There are many statues and memorials in Dublin, New York and other cities in memory of the famine. The fields of Athenry is a famous song about the great famine and is often sung at national team sporting events in memory and homage to those affected by the famine.

The Great famine is one of the biggest events in Irish history and is ingrained in the identity on the nation to this day. It was a major in factor in Irish Nationalism and Ireland's fight for Independence during subsequent rebellions. As many Irish people felt a stronger need to regain Independence from English rule.

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After the Irish War of Independence (1919–1921) the Anglo-Irish Treaty was signed which led to the formation of the semi-independent Irish Free State (now the independent Republic of Ireland) which consisted of 26 counties in the south and Donegal in the North-West. The remaining six counties in the northeast remained in the United Kingdom as Northern Ireland. It is predominately religion, historical, and political differences that divide the two communities of (nationalism and unionism). Four polls taken between 1989 and 1994 revealed that when asked to state their national identity, over 79% of Northern Irish Protestants replied "British" or "Ulster" with 3% or less replying "Irish", while over 60% of Northern Irish Catholics replied "Irish" with 13% or less replying "British" or "Ulster".[68] A survey in 1999 showed that 72% of Northern Irish Protestants considered themselves "British" and 2% "Irish", with 68% of Northern Irish Catholics considering themselves "Irish" and 9% "British".[69] The survey also revealed that 78% of Protestants and 48% of all respondents felt "Strongly British", while 77% of Catholics and 35% of all respondents felt "Strongly Irish". 51% of Protestants and 33% of all respondents felt "Not at all Irish", while 62% of Catholics and 28% of all respondents felt "Not at all British".[70][71][citation needed]

In the Republic of Ireland, as of 2011, 3,861,335 people or about 84.16% of the population are Roman Catholic.[72] In Northern Ireland about 41.6% of the population are Protestant (19.1% Presbyterian, 13.7% Church of Ireland, 3.0% Methodist, 5.8% Other Christian) whilst approximately 40.8% are Catholic as of 2011.

The 31st International Eucharistic Congress was held in Dublin in 1932, that year being the supposed 1,500th anniversary of Saint Patrick's arrival. Ireland was then home to 3,171,697 Catholics, about a third of whom attended the Congress.[73][74] It was noted in Time Magazine that the Congress' special theme would be "the Faith of the Irish."[73] The massive crowds were repeated at Pope John Paul II's Mass in Phoenix Park in 1979.[75] The idea of faith has affected the question of Irish identity even in relatively recent times, apparently more so for Catholics and Irish-Americans. Today the majority of Irish people in the Republic of Ireland identify as Catholic, although church attendance have significantly dropped in recent decades. In Northern Ireland, where almost 50% of the population is Protestant, there has also been a decline in attendances.

What defines an Irishman? His faith, his place of birth? What of the Irish-Americans? Are they Irish? Who is more Irish, a Catholic Irishman such as James Joyce who is trying to escape from his Catholicism and from his Irishness, or a Protestant Irishman like Oscar Wilde who is eventually becoming Catholic? Who is more Irish... someone like C.S. Lewis, an Ulster Protestant, who is walking towards it, even though he never ultimately crosses the threshold?[76]

This has been a matter of concern over the last century for the followers of nationalist ideologists such as DP Moran.

Thomas Davis, a prominent Protestant Irish nationalist who founded the Young Ireland movement, identified the Irish as a Celtic nation.[77] He estimated that ethnically, 5/6ths of the nation were either of Gaelic Irish-origin, descended from returned Scottish Gaels (including much of the Ulster Scots) and some Celtic Welsh (such as his own ancestors and those carrying surnames such as Walsh and Griffiths).[77] As part of this he was a staunch supporter of the Irish language as the "national language".[77] In regards to the Germanic minority in Ireland (of Norman and Anglo-Saxon origin) he believed that they could be assimilated into Irishness if they had a "willingness to be part of the Irish Nation."[78]

History and geography have placed Ireland in a very special location between America and Europe... As Irish people our relationships with the United States and the European Union are complex. Geographically we are closer to Berlin than Boston. Spiritually we are probably a lot closer to Boston than Berlin. – Mary Harney, Tánaiste, 2000[79]

The Irish diaspora consists of Irish emigrants and their descendants in countries such as the United States, Great Britain, Canada, Australia, New Zealand, South Africa, and nations of the Caribbean such as Jamaica and Barbados. These countries all have large minorities of Irish descent, who in addition form the core of the Catholic Church in those countries.

Many Irish people were also transported to the island of Montserrat, to work as indentured servants, exiled prisoners or slaves. Unlike Africanchattel slaves, the majority of Irish labourers who were sent to Montserrat did so by personal choice although they were tricked into doing so by the promise of payment and land of which they did not receive.[80] Some were exiled by the English Oliver Cromwell due to the large Irish population and their attempted rebellion on 17 March 1768. To this day, the Island celebrates St. Patrick's Day as a public holiday to commemorate the event.[81] People of Irish descent also feature strongly in Latin America, especially in Argentina and important minorities in Brazil, Chile, and Mexico. In 1995, President Mary Robinson reached out to the "70 million people worldwide who can claim Irish descent."[82] Today the diaspora is believed to contain an estimated 80 million people.[83]

During the 18th and 19th centuries, 300,000 free emigrants and 45,000 convicts left Ireland to settle in Australia.[102] Today, Australians of Irish descent are one of the largest self-reported ethnic groups in Australia, after English and Australian. In the 2006 Census, 1,803,741 residents identified themselves as having Irish ancestry either alone or in combination with another ancestry.[103] However this figure does not include Australians with an Irish background who chose to nominate themselves as 'Australian' or other ancestries. The Australian embassy in Dublin states that up to 30 percent of the population claim some degree of Irish ancestry.[104]

It is believed that as many as 30,000 Irish people emigrated to Argentina between the 1830s and the 1890s.[8] This was encouraged by the clergy, as they considered a Catholic country, Argentina, preferable to a Protestant United States. This flow of emigrants dropped sharply when assisted passage to Australia was introduced at which point the Argentine government responded with their own scheme and wrote to Irish bishops, seeking their support. However, there was little or no planning for the arrival of a large number of immigrants, no housing, no food.[105] Many died, others made their way to the United States and other destinations, some returned to Ireland, a few remained and prospered. Thomas Croke Archbishop of Cashel, said: "I most solemnly conjure my poorer countrymen, as they value their happiness hereafter, never to set foot on the Argentine Republic however tempted to do so they may be by offers of a passage or an assurance of comfortable homes."[106] Some famous Argentines of Irish descent include Che Guevara, former president Edelmiro Julián Farrell, and admiral William Brown. There are people of Irish descent all over South America, such as the Chilean liberator Bernardo O'Higgins and the Peruvian photographer Mario Testino. Although some Irish retained their surnames intact, others were assimilated into the Spanish vernacular. The last name O'Brien, for example, became Obregón.

^The figure 1,250,000 is mentioned on the commemorative stone at the Papal Cross in the Phoenix Park, Dublin; a quarter of the population of the island of Ireland, or a third of the population of Republic of Ireland

^Cole, Patrick (29 March 1889). "Irish Emigrants to the Argentine Republic". Western Daily Press. Retrieved 29 November 2015 – via British Newspaper Archive. (Subscription required (help)). It is a sad and pitiable sight to see Irish mothers with, in some cases, their dying babes in their arms ... ... in many cases mothers sold their clothing from their backs to procure food for their starving children